Chromosome Meiotic Behaviour and Ploidy Nature in Genus Ocimum (Lamiaceae), “Sanctum Group”

抄録

Meiotic studies in five species alongwith their different races/morphotypes of “Sanctum group” of Ocimum were made from pollen mother cells. The investigated taxa include one tetraploid (2n=4x=32), two pentaploids (2n=5x=40), one hexaploid (2n=6x=48) and one octoploid (with 2n=8x=64) species with basic chromosome number as x=8. The chromosomes in all the species were multiple of x=8 chromosomes. Meiosis was normal but for forming few loose bivalents anf few nuivalents. Anaphase segregation was regular with perfect fertility rate. The mean chiasma frequency per PMC and per bivalent has been studied. It was suggested that lack of multivalents formations in these polyploid species was due to short size of chromosomes having low chiasma frequency, established nature of polyploids and also other genic factors. Two base numbers x=8, 12 are suggestive for the genus Ocimum as a whole i.e. x=8 for “Sanctum group” and x=12 for “Basilicum group”.